As lighting apparatuses for vehicles that emit amber color light, for example, direction indicators, those comprising electric bulbs colored in an amber color have been conventionally used. However, as those overcoming the drawbacks of electric bulbs, i.e., high power consumption and restriction on design for smaller size, those utilizing LEDs have been proposed and practically used.
As amber color LEDs, there are known AlGaInP semiconductors and GaAsP semiconductors showing an emission spectrum in the range of about 580 to 610 nm. However, these LEDs have a drawback that luminescence intensity thereof markedly decreases, as the ambient temperature becomes higher. For this reason, for use suffering from high ambient temperature such as rear combination lamps, a large number of amber LEDs must be provided in order to obtain required quantity of light, which leads to restriction on design of lighting apparatuses concerning increase in cost and reservation of installation space. Moreover, since turn signal lamps incorporated into headlamps locate near engines, and thus are exposed to especially high ambient temperature, required quantity of light cannot be secured with the aforementioned amber LEDs.
There have also been proposed lighting apparatuses that realize an amber color by a combination of a blue LED and a fluorescent substance that emits light of a long wavelength upon excitation with light emitted by the LED (Patent document 1). Patent document 1 describes use of (Ca,Sr)2Si5N8:Eu as the fluorescent substance for long wavelength to be combined with a blue LED.
However, since this fluorescent substance shows a full width at half maximum of about 100 nm, and emits a lot of long wavelength components of low visibility, it suffers from a problem of low efficiency. Moreover, since it shows a persistence characteristic, it suffers from a problem that afterglow in non-emitting periods reduces visibility when it is used with blinking. Furthermore, an optical filter is indispensable for the amber color lighting apparatus described in Patent document 1 for shielding light emitted by LED.                Patent document 1: Japanese Patent Unexamined Publication (KOKAI) No. 2005-123165        